1. Field of the Invention
The present invention relates to an elastic wave resonator in which an interdigital transducer electrode is provided on a piezoelectric substrate, and to an elastic wave filter and duplexer including such an elastic wave resonator.
2. Description of the Related Art
Conventionally, elastic wave resonators are widely used as resonators defining band-pass filters included in cellular phones and the like. Japanese Unexamined Patent Application Publication No. 2-295212, for example, discloses an elastic wave resonator including a piezoelectric substrate and an interdigital transducer electrode provided on the piezoelectric substrate. Japanese Unexamined Patent Application Publication No. 2-295212 discloses that the interdigital transducer electrode is made of Al film.
However, forming the interdigital transducer electrode from Al film as in the elastic wave resonator according to Japanese Unexamined Patent Application Publication No. 2-295212 has caused a decrease in the linearity of signals. There have thus been cases, when using the elastic wave resonator according to Japanese Unexamined Patent Application Publication No. 2-295212 in a transmission filter of a duplexer, where the level of non-linear signals emitted from the transmission filter increase and cause a decrease in the reception sensitivity.